What Makes A Boat Seaworthy?

What makes a boat seaworthy?

It’s a seemingly simple question, but one with many, not always so simple answers. By definition, seaworthy simply means that a vessel must be in good enough condition to sail on the sea. But as to what exactly defines “good enough” condition — and what specific features and trails to look for — that’s not always so obvious.

Let’s try to eliminate the confusion with some real-world examples of seaworthiness.

Does It Float…And Will It Stay That Way?

The obvious starting point would be to ensure that any boat does what a boat is, at its essence, designed to do — stay afloat. That means the hull should have no structural damage that could let water intrude, no leaky or improperly bedded fittings below the waterline, no worn out hoses or missing clamps in the engine compartment, even something as simple as a properly fitted drain plug…that hasn’t been left in a cupholder or your tow vehicle.

Working outwards from there, consider the boat builder’s design choices. Look closely at the freeboard, the distance between the waterline and the deck or top of the gunwales on smaller craft. There should be no points low enough to let water come over the sides during normal, responsible operation. That includes the boat not taking significant water over the transom when backing down hard under throttle, not ducking the bow under large wakes when fully loaded and turning to pick up a downed skier or wakeboarder, and not dipping a gunwale into the water when rocking side to side in larger wakes or waves or when passengers suddenly switch sides.

Remember, these details should be considered when the boat sits in the water at the dock, but most important is how the boat behaves in open water when loaded with passengers, fuel, water and various other gear you’ve brought aboard.

Any thru-hull fittings demand closer inspection. Fittings, especially those that penetrate the hull below the waterline, should be tightly secured, caulked, internal hoses tightly clamped (ideally with double clamps in below-waterline applications) and connected to quality seacocks that can be closed in the event of an emergency. Check out the standards published by the American Boat and Yacht Council for specifics on both thru-hull fittings and seacocks; all are definitely not created equal. Also, make sure seacocks are readily accessible, so that you or your crew can reach them quickly and easily in the event of a problem.

Draining Water And Self-Bailing Boats

Another consideration should be just how efficiently and quickly water that does make it aboard is removed. Smaller boats often simply drain the deck to the bilge, leaving it up to your bilge pumps to get that water back overboard. Larger boats typically feature self-bailing cockpits, with scuppers and drain lines to funnel that water overboard. Are they big enough to handle the water that may make it aboard? Smaller scuppers will limit the speed at which water flows into the drain lines. Smaller diameter drain lines (less than 1 1/2”) are susceptible to clogging from debris.

Boats Can Sink Very Quickly

Why focus so much on preventing a boat from taking on, or holding water? Because it doesn’t take much of it to cause a serious, even potentially deadly situation. Here’s a frequently quoted statistic — just one two-inch hole punched six inches below the waterline will allow a whopping 55 gallons a minute (or over 3,000 gallons per hour) to flow into your hull. With that in mind, consider the tiny 500 gallon-per-hour pumps often found in many runabouts, or even the multiple, higher-capacity pumps on larger vessels. For starters, their actual output is typically far less than the ideal they’re rated for. And contrary to popular opinion, they’re not really designed to get rid of much more than nuisance water, or to slow the flow of water long enough for occupants to prepare to abandon ship.

And if you think your boat won’t actually sink, think again. Only boats less than 20’ in length are actually required by the Coast Guard to have level floatation — typically from added foam floatation or, to a lesser extent, below-deck compartmentation — when swamped. While a number of flagship brands go above and beyond to provide that floatation above 20’, most do not.

Boat Stability

Beyond simply staying afloat, a seaworthy boat should also be stable, both at rest and under power in the most extreme conditions you intend to run it in.

In real world terms, consider how the boat will behave in various scenarios. On a smaller boat, check to see the result of a sudden shift in the location of passengers, such as when guests spot a dolphin and go clamoring to one side. In open water, pay attention to how wakes, waves and even the wind can rock the hull from side to side, or even bow to stern, both at rest and underway.

If you’re in bigger water, consider what would happen if a sizable amount of water made it onto the deck, how that added, moving weight would affect the stability, and how quickly the boat is designed to get that water overboard. The key is to find a boat that handles these forces well enough to, at minimum, keep your passengers comfortable and safe and, in the worse case scenario, prevent your boat from listing far enough to threaten passengers safety, or even capsize.

Obviously, the smaller the boat and the larger the influences, the more susceptible it typically is to these forces but keep in mind modifications can also negatively affect stability. Repowering your boat with newer, typically lighter engines below or adding a tower above raise the boat’s center of gravity and can reduce stability.

Match Your Boat To The Body Of Water: Be Realistic

A seaworthy boat should also always be a match to the body of water you intend to operate on. Be realistic about your vessel and its capabilities. Smaller boats may be great for most lakes and rivers, but larger bodies of water — and the larger winds and waves that are common on them — will quickly prove overwhelming. Smaller craft lack the overall size, freeboard, and yes, stability to handle more extreme conditions.

Larger boats may be better equipped to handle these conditions simply because of their increased length and beam, but need to be better prepared for the more extreme possibilities the environment presents. Hulls should be designed with enough vee to cut through larger waves; construction should be more robust to handle the increased stress; should you venture far from shore, a redundant power source might make the difference between being stranded and making it back to the dock. Any size boat should also handle responsively, and have adequate horsepower to handle changing water conditions and deliver a ride that keeps passengers not only comfortable but safe and relatively dry.

Other Items To Consider

Last but most certainly not least, consider the often overlooked items that contribute to a boat’s seaworthiness. Is the battery (or batteries) fully charged, in good condition, free of corrosion on the terminals and ready to start the craft without hesitation when needed? Similarly, is the engine reliable, in good tune and have adequate oil and cooling? Do all lights and horn work, and have you recently tested the bilge pump(s)? Is the steering responsive and in good order? Is your passenger load within the manufacturer’s capacity rating? Even something as simple as the captain’s visibility, both underway and when powering onto plane, can play a role in the boat’s practical seaworthiness.

Written by: Jeff Hemmel

Jeff Hemmel writes for boats.com, Boating, PersonalWatercraft.com, and Powersports Business. The former Senior Editor at Watercraft World, Jeff is a multi-time award winner as well as a 2008 inductee into the IJSBA Hall of Fame. His first book, "The Anti-Pirate Potato Cannon...and 101 Other Things For Young Mariners To Try, Do, & Build On the Water," received a bronze medal in the 2010 Moonbeam Children's Book Awards. For more info, visit Jeff Hemmel's website.